1. Field of the Invention
The present invention relates to an image forming device such as a copying machine, a printer, a facsimile, a multi-function device which combines all these functions, and the like, and an image reading device employed in the image forming device which reads an original that has been automatically conveyed thereto.
2. Background Information
Conventionally, an image reading device which reads an image of an original being automatically conveyed from a predetermined original tray to a conveyance path by an automatic conveying device is well-known. In addition, some image forming devices are provided with an image reading device.
A halogen lamp, a xenon lamp, a fluorescent lamp or the like is generally used as a light source of an exposure lamp for reading an image in the image reading device. However, it is known that the light intensity of such light source varies with elapsed lighting time. The term “elapsed lighting time” has two meanings: the cumulative lighting time, and the total time from the point in which the light is turned on until the light is turned off. In the former situation, the light intensity varies due to deterioration of the exposure lamp, and in the latter situation, the light intensity varies because of an increase in temperature upon the lighting of the exposure lamp.
In situations where a plurality of originals (e.g., a document having a plurality of pages) are continuously read, the exposure lamp is kept on. However, if the light intensity varies as described above, the image data will also vary depending on the original, and thus suitable image data cannot be output. Furthermore, the exposure lamp is kept on after the previously read original is read until the next original is read, that is, the exposure lamp is on even when it is not necessary. As a result, the exposure lamp needlessly deteriorates and power is wasted.
Shading correction may be performed as a method of eliminating the influence of the variation in light intensity on the image data. In addition, in order to eliminate unnecessary lighting of the exposure lamp, controlling the image reading device such that the exposure lamp is turned off at a predetermined timing has been attempted.
In addition, in situations in which a large memory capacity is required for color originals and the like, because it will take time to transfer image data in an image memory to a hard disk, or to maintain the image memory for reading after printing is completed, a period of time will elapse from the point at which reference data is obtained for shading correction until the point at which the reading is actually started. An image reading device described in Japanese unexamined patent publication number 2002-330269 tries to solve this type of problem. In other words, because the light intensity will vary after the reference data is obtained in the above situation, in this image reading device, after shading correction, the exposure lamp will be turned off when the cumulative time needed to read an original exceeds a predetermined time, and a shading correction will be performed again at the point at which an original is to be read.
One of the printing modes in an image forming device is a group-copy mode. In the group-copy mode, each time an original set on an original tray of the image reading device is automatically conveyed and read, a predetermined number of pages of image data that corresponds to the original will be printed. In the group-copy mode, because each original will be printed, only one page of image data will be stored in the image memory at a time. Therefore, the image memory can be reduced in situations in which an original has a large number of pages, or when color images or high image quality is required. However, in the group-copy mode, after image data for a particular original is read and output to the image memory, the exposure lamp will be kept on while a predetermined number of pages are printed even though the reading of the next original has not started.
In addition, in some image forming devices, when there are originals that have a large number of pages, image data will be printed every time a predetermined number of pages of the original are read. In this situation as well, because only image data for a predetermined number of pages are stored in the image memory, the image memory required can be reduced. However, the exposure lamp will be kept on while the image data for the predetermined number of pages stored in the image memory is printed, and until the reading of the next predetermined number of pages is started. Here, in situations in which there are two or more printing units, the exposure lamps will be on for an unnecessarily long period of time.
This is true not only in situations in which the image data is to be printed, but also in situations in which other image data processing, such as facsimile transmission, is to be performed, and situations in which image data is to be registered in a database of a server and the like. In other words, the same problem will occur in situations in which: (1) every time an original is read, the corresponding image data is simultaneously transmitted to a plurality of facsimile devices (simultaneously registered in a plurality of databases); (2) every time a predetermined number of pages of an original are read, the image data is transmitted to a facsimile device (registered in a database); and (3) every time a predetermined number of pages of an original are read, the image data is simultaneously transmitted to a plurality of facsimile devices (simultaneously registered in a plurality of databases).
In addition, while a plurality of originals are continuously read and the image data is processed (printed, transmitted to a facsimile or registered in a database), there will be situations when the exposure lamp is needlessly kept on due to the processing means of the image forming device. More specifically, in situations in which a lack of toner is detected, in situations in which a facsimile calls, in situations in which a connection confirmation to a server is performed, in situations in which the device enters a periodic image processing adjustment mode (e.g., current adjustment for the charging device, toner density adjustment, fixing temperature adjustment, etc.), and the like.
Therefore, the exposure lamp is kept on for a long period of time due to the aforementioned image data processing mode and the aforementioned processing means, which causes image deterioration and increases power consumption. These problems are not solved in the image reading device described in Japanese unexamined patent publication number 2002-330269. In this prior art reference, because only the time needed to read an original is measured, in situations where the exposure lamp is kept on while no reading operation is being performed as described above, the exposure lamp will be unnecessarily kept on and the cumulative lighting time will increase.
The present invention is made in view of the above problems, and it is an object of thereof to provide an image reading device that controls variation in light intensity that occurs during the time in which an exposure lamp (a light source for reading an original) is lit, prevents deterioration of a read image, and prevents wasteful power consumption.
In addition, it is another object of the present invention to provide an image processing system and an image forming device that controls variation in light intensity that occurs during the time in which an exposure lamp (a light source for reading an original) is lit, prevents deterioration of a read image, and not only obtains suitable printed material, transmission data, or registration data, but also prevents wasteful power consumption.